Screen for paper-pulp.



Patented Mar. 4, 1902.

' S. H. TIBBETTS.

SCREEN F08 PAPER PULP.

(Application filed July 1, 1901.)

2 Shuts-Sheet I.

(No Model.)

INVENTORI v 7i 56223.

WITNESSES A TTORNEYS No. 694,900. Patented Mar. 4, I902.

s. H. TIBBETTS.

SCREEN FOB PAPER PULP. E

(Applies-tic! filed July 1', 1901. (No Model.) E 2 Sheets-Sheat 2.

-llllllllllllllllllIHlllllllllllllll Clllllmlillllllllllimlllllllllllllmll Q 2 WITNESSES: m VENTOH 45 arecontained.

. UNITED STATE 'FATENT OFFICE.

ONE-HALF TO EDWARD E. TIBBETTS, OFGROVETON, NEW? H AMPS HIRE.

SCREEN FOR PAPER-Pu LP.

SPECIFTGATION forming part of Letters Patent N0. 694,900, dated March 4,1902. Application filed July 1, 1901. Serial No. 66,786. (No model.)

To all whom it may concern:

Be it known that I, SETH HU'rOHINs TIB- BETTs, of Groveton, in thecounty of Goosand State of New Hampshire, have invented a new and usefulImprovement in Screens forPaper- Pulp, of which the following is aspecification.

My invention comprises a new means for fastening screen-plates in thecradle of a paper-pulp screen without the aid of screws;

1 o In practice there are usually from two to three of these screens toeach paper-machine for screening the stock that the paper is made from,and in pulp-mills a great many of these screens are used in cleaning thestock and r5 fitting it for the paper-mill. In each one of these screensthere are usually ten plates. The most common size of these plates istwelve by forty inches and about one-half inch thick, made of bronzemetal. To fasten one of these plates properly requires thirtyone-and-onehalf-inch screws, so that a screen with ten plates requiresthree hundred screws to fasten the plates in the cradle. In practice itis called a days work for a man to take out the '25 old plates andinsert new ones in two of these There is also another difliculty thatscreens. is caused by using screws and that is that the cross-piecesthat the plates are fastened to soon wear out by turning in and outthese screws and have to be renewed quite often.

These plates have to be changed every two or three weeks, and thiscauses much trouble, owing to the time it takes to change them, the

embarrassment that the screws give in break-. ing off, and loosenessfrom the wearing of the holes, so that the screws do not hold. Myinvention is designed to obviate the difficulty referred to, since itwill not take one-tenth of the time to change the plates as it will bythe old way and the cross-pieces will not have to be renewed, as no wearcomes on them, as in the old way.

Figure 1 is a perspective view,partl y broken away, of the cradle inwhich the screen-plates Fig. 2 is a partial longitudinal section throughthe screen. Fig. 3 is a detached side view of one of the retainingbarsfor the screen-plate. Fig. t is a similar view of one of the cross-barsof the cradle above and to which the retaining-bar is secured. Fig. 5 isa perspective view of one of the screen-plates. Fig. 6 is across-section on line 6 6 of Fig. 2. Fig. 7 is a detail of themortise-plate.

In the drawings, X represents the cradle, in whose bottom are arrangedcross-pieces A each formed on its upper surfaces with two dovetailnotches o. v

- D represents the retaining bars, one of which is located immediatelyabove and parallel to each cross-piece A, and M represents thescreen-plates, which are arranged transversely to the cradle and areheld in by the retaining-bars D. The only difierence be-. tween the newplate and the old is that on the new one there is a lip on each lowerside of the plate. (Shown by the letter B, Figs. 2 and 5.) This lip, asshown, is made tapering or wedge shape. The retaining-bar has formedalong its upper edges overhanging lips E atan inverse angle to those onthe plates. On the bottom of'this bar are two dovetail tenonsF, whichfit in the dovetail notches 0, Fig. 4., of. the cross-pieces A. Theretaining-bar is made a little longer than the plates which it fastens,and its ends G fit in the mortise C, Fig. 1, in the sides of the ore.-dle. The mortises are in the nature of metal pockets, Fig. 7, made withtheir chambers in the form of an arc and so placed that the convex partcomes over the center of each crosspiece A, Fig. l, and have a cam-likeaction in securing and tightening the ends of said bars. These mortisesare made convex and so placedthat the lowest part is just the rightheight to press the ends of the retaining-rods firmly down on thecross-pieces A, and in re moving the retaining-bar when the bar is movedsidewise the mortise loosens up its cam-like grip and makes iteasier toremove the said bar. The mortises are made deeper horizontally than theend pieces G arelong, so when the retaining-bar is moved sidewiseenough, so that the tenons F F clear the notches o 0, then by pushingthe retainingbar endwise a little one end will go in deeper into onemortise and clear the other, so it can be taken out. The function ofthis simple arrangement will be understood by referring to Fig. 2.

The letters M M show the cross-section of the plates, and D theretaining-bar. To assemble these plates in the cradle, one of the platesM is placed in one end of the cradle and then one of the retaining-barsD. I put one end of the latter in a mortise O and push it far enough, sothat the near end will pass down in the cradle, and then pull the bar,so that the near end will pass into the mortise on the near side; thenadjust the bar endwise, so that the tenons F F will be opposite thenotches 0 0; then push it sidewise, so that thelip E will pass over thelip B. This, owing to the ends of the retaining-bar being in themortises and the dovetails tenons F F in the notches 0 0, will hold thatside of the plate firmly down. Then take another plate M and push thelip B under the lip E of the retaining-bar, then another bar, then aplate, and so on until all of them are in. In each end of the cradle areset-screws S, arranged in the plane of the plates. After the plates andretaining-bars are all in the tightening up of these set-screws willpress the plates and bars into a smooth and solid bottom, and the morepressure on the set screws the tighter they will hug to the pieces A. Oneach side of a notch 0 there is a piece of metal N, fastened on thewood, so that they can be adjusted to take up any wear that might takeplace.

Underneath the cradle is arranged machinery for producing a downwardsuction, (not shown,) which pulls the pulp down through the narrow slitsin the screen-plates, and also gives an upward pressure, which forcesaway any dirt that covers the slits'in the plates, working somethinglike a vacuum-pump. If the screen-plates are not firmly held down andtight, dirt would work through, and dirty paper would be the result. Asthe pulp-stock goes in the cradle over the top and passes the wholelength of the screen, it is important that the plates and fasteningsshould be so constructed that they give a practically smooth bottom;otherwise as the stock passes from one end to the other it would bank upand soon stop up all the slits in the plates. My invention fullyprovides for these conditions.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is

1. A screen comprising a main frame or cradle having in its bottomcross-bars with undercut notches, retaining-bars having on their lowersides tenons corresponding to said notches and having overhanging upperedges, and screen-plates having lips along theirlower edges adapted tobe caught and held by the retaining-bars substantially as described.

2. A screen comprising a main frame or cradle having in its bottomcross-bars with undercut notches, retaining-bars having on their lowersides tenons corresponding to said notches and having overhanging upperedges, tightening devices for the ends of the retaining-bars, andscreen-plates having lips along their lower edges adapted to be caughtand held by the retaining-bars substantially as described.

3. A screen comprising a main frame or cradle having in its bottomcross-bars with undercut notchesand mortises in the sides of the cradleimmediately above each crossbar, retaining-bars having on their lowersides tenons corresponding to said notches and overhanging upper edges,the ends of said retaining-bars being seated in said mortises, andscreen-plates having lips along their lower edges adapted to be caughtand held by the retaining-bars substantially as described.

4. A screen comprising a main frame or cradle having in its bottomcross-bars with undercut notches and mortises in the sides of the cradleimmediately above each end of the cross-bar, retaining-bars having ontheir lower sides tenons corresponding to said notches and overhangingupper edges, the ends of said retaining-bars being seated in saidmortises and the mortises being made of a greater horizontal depth thanthat occupied by the fixed position of the retaining-bars, so as topermit the retaining-bars to be entered by an endwise movement, thendrawn back, and moved laterally to seat the tenons in the notches, andscreen-plates having lips along their lower edges adapted to be caughtand held by the retaining-bars, substantially as and for the purposedescribed.

5. A screen comprising a main frame or cradle, having in its bottomcross-bars with undercut notches, retaining-bars having on their lowersides tenons corresponding to said notches and overhanging upper edges,camlike tightening-seats for the ends of the retaining-bars arranged toforce the ends of the said bars down when the bar is moved laterally toa position above the cross-bars, and screen-plates having lips alongtheir lower edges adapted to be caught and held by the retaining-barssubstantially as described.

6. A screen comprising a main frame or cradle having in its bottomcross-bars with detachable retaining-bars above them, saidretaining-bars having overhanging edges, detachable screen-plates havinglips along their lower edges adapted to be caught and held by theretaining-bars, and set-screws at the ends of the cradle arranged in theplane of the screen-plates and adapted to bear against and tighten thesame substantially as described.

7. A screen comprising a main frame or cradle having in its bottomcross-bars with detachable retaining-bars above them, said retainingbars having overhanging edges, screen-plates having lips along theirlower IIO taining-bars together with a tightening action substantiallyas described.

SETH HUToHINs TIBBETTS;

Witnesses:

PHILL S. TIRRILL, E; E. TIBBETTS.

